I just did a rear wheel for a kdx I bought recently. Bought the tusk stand on sale because I had swing arm off the bike.
Really liked the stand. Well worth the $60. I've trued and set off set on swing arm or forks previously, but the stand is nice.
Same deal. I used a new tusk impact rim and Buchanan supplied the spokes.
Putting wheels together is actually kinda fun

Don't know what factory offset is.I do know when I did the super motor wheels for my E conversion I needed to go basically as far as I could.
The spokes will contact the caliper if offset too much.
Your best bet may be just moving it over until you have enough clearance between tire and chain.
If you change offset, its a good idea to remove tire and make sure the spokes aren't protruding thru the rim, which could result a flat tire

fwiw I've had e model tank then switched to the IMS 2.6 gallon tank for e model on an S for about 9000 off road miles with no problems.
Plenty of crash testing,even high speed crash testing.3 hare scrambles
I,'ve switched from a hard mount at the back to using the e model one strap.
Also running una biker rad guards

The only scenario I can think of where a cam swap would result in increased oil consumption would be if one or both exhaust valves were shimmed in such a way where there was less than zero clearance, resulting in exhaust valve not fully seating and letting oil by

Change shims to bring them into spec.. I like low end of spec..
re check next oil change.
Probably not worth the shim kit, unless u plan on keeping for life.
Bought my' 04 S used late 2004 with about 1100 miles on it and one intake was slightly u/s